Batteries are used in a wide variety of fields, e.g., as the power source of electronic equipment such as mobile phones or notebook PCs, or of vehicles such as hybrid cars or electric cars. Batteries include nickel cadmium batteries, nickel metal hydride batteries, and lithium ion secondary batteries.
In applications as the power source for various purposes, it is common to use batteries as a battery module assembled by electrically connecting a plurality of cells to obtain a power output in accordance with the purposes of use. For example, a plurality of cells is electrically connected in series to provide a necessary output voltage in a battery module used as the power source of a vehicle. In this case, from a viewpoint of saving installation space in the vehicle, it is common to use a battery module having a plurality of rectangular cells arranged side by side. Heat radiation, as well as electrical and thermal insulation between adjacent cells need to be taken into consideration for a battery module having such a cell arrangement.
Patent Document 1 is one example relating to such a technique. Patent Document 1 discloses a battery module in which a plurality of rectangular cells is arranged side by side with spacers interposed between adjacent cells, the spacers being made of an insulating resin containing a foaming agent that reacts to heat above a certain temperature and is thermally decomposed. Thus, while insulating adjacent cells from each other, the spacers allegedly suppress heat conduction between adjacent cells in the event of an abnormal temperature rise in one of the cells of the battery module. Patent Document 1 also discloses that passages for heat exchange medium are formed in the spacers. This allegedly enables efficient temperature adjustment of the battery module.